As the price of light emitting diode (LED) lamps decrease they become more attractive of use in lighting, with further advantages over prior technology incandescent and fluorescent lamps of longer useful life and lower power consumption. Many millions of commercial and industrial lighting fixtures use fluorescent lamps that would greatly benefit by using LED lamps to replace these fluorescent lamps. However, the vast majority of these fluorescent lighting fixtures require a modification to made thereto when LED lamps are installed therein, e.g., bypass the lighting ballast. Some newer LED lamps have been designed to replace fluorescent lamps with certain types of ballasts without having to rewire the fixture, but not all ballasts, generally only instant start ballasts. Removal and/or rewiring of a fluorescent lamp ballast is not difficult but is a hazardous activity since high voltage may be present. This removal work typically requires a qualified electrician.
An example of a simplified fluorescent lighting fixture circuit is shown in FIG. 1. The fluorescent lamp circuit operation can be understood as two states of operation: 1) Lamp Preheat/Start and 2) Lamp Running. The purpose of the Preheat State on the fluorescent lamp 102 is to ionize the rarefied gas present in the lamp 102. There are typically two filaments 106 and 116, one at each end of the fluorescent lamp 102 (a glass tube with a phosphorescent coating on the inside surface of the glass tube. When the preheat starter switch 104 is closed, Current from an AC source 114 flows through the filaments 106 and 116. The application of current through the filaments 106 and 116 heats them, and so, ionizes the gas surrounding them. Also, because there is an inductor 112 in series with the filaments 106 and 116, the AC current flows through the inductor 112 as well. This inductor 112 is typically called a ballast in this art. When the preheat starter switch 104 is opened, current across the filaments 106 and 116 will cease. But by Faraday's Law of Magnetic Induction, any current that was flowing through the inductor 112 (ballast) cannot instantaneously cease. The collapsing magnetic field in the inductor 112 will cause current to still flow. The voltage across the inductor 112 will rise in order to accommodate this law of physics. Since the gas in the lamp has been partially ionized during the Preheat State, it is conductive. The rising voltage from the inductor 112 will start the current flow across the ionized gas in the lamp 102, from end to end. This event is called “Striking the Lamp” in this art. Basically an arc through the ionized gas is created to allow the inductor 112 to continue its current flow. Once current flows across the entire lamp 102, the gas becomes fully ionized, and AC current flows continuously across it. In this “Running State,” the inductor 112 is used for its other purpose, to limit the lamp current.
The previous description was for a magnetic ballast used in fluorescent lamp circuits. There are a number of other more complex fluorescent ballast designs in the art. The many innovations already developed for this technology and currently available in the lighting market allow for smaller ballast designs, better energy efficiency, higher lamp start reliability (including re-starting the lamp if it went out), lamp dim-ability, lamp flicker avoidance, ballast buzz noise avoidance, and many safety related features involving damaged or ‘burnt-out’ lamps. But they all have one thing in common: There is always a ‘black box’ in the fluorescent lamp fixture called a “ballast.” This ballast device starts the lamp and drives the lamp with a limited current while it is on.
The LED replacement lamps available today require a modification to the wiring in the fluorescent lamp fixture. The single reason for this is that the current state of the art in LED replacement lamp technology does not emulate the behavior of fluorescent bulbs adequately enough for the ballasts to drive them correctly. Many LED replacement lamp vendors have disclaimers on their products that have statements like this:                1) Clip and tie off <a particular> ballast wire in the fixture to allow this replacement lamp to work correctly in your existing fluorescent lamp fixture.        2) The ballast must be removed and the fixture rewired for proper operation.        3) This lamp works with Instant Start Ballasts only. Removal of the existing ballast and rewiring of the fixture is required if not using an Instant Start Ballast.        
There are also warnings on many LED replacement lamp products that state that any rewiring of the fixtures should be performed only by a qualified service technician. These restrictions on the usability of these replacement lamps inhibit their wide market acceptance. This market is in need of a technology that allows an LED replacement lamp to be manufactured so that ballasts designed for standard hot cathode fluorescent lamps operate correctly with the LED lamp replacement.